French Onion & Celeriac Soup: A Flavorful Twist on a Classic

French onion soup is a timeless classic, a culinary comfort blanket that warms you from the inside out. The rich, savory broth, the sweet caramelized onions, the crusty bread, and the bubbly, melted cheese – it’s a symphony of flavors and textures that’s hard to resist. But what if we took this beloved dish and gave it a slightly unexpected, yet utterly delicious, twist? Enter celeriac, the humble root vegetable that adds a subtle earthy sweetness and a delightful creaminess to the soup. This French Onion & Celeriac Soup is a sophisticated upgrade on the original, perfect for a cozy night in or a special occasion.

## Why Celeriac?

Celeriac, also known as celery root, is often overlooked in the vegetable aisle. However, this knobbly, unassuming root is a powerhouse of flavor and nutrition. It has a delicate celery-like taste with hints of parsley and a slightly nutty sweetness. When cooked, it becomes incredibly tender and creamy, making it an excellent addition to soups and stews. In this French onion soup variation, celeriac complements the sweetness of the caramelized onions beautifully, adding depth and complexity to the broth. It also adds a lovely creamy texture without the need for excessive amounts of cream.

## Ingredients You’ll Need

Before we dive into the recipe, let’s gather our ingredients. You’ll need:

* **Onions:** Yellow onions are the traditional choice for French onion soup, but you can also use a combination of yellow and sweet onions for a more nuanced flavor. We will need about 3 pounds of onions, which equals roughly 5-6 medium-sized onions. Patience is key when caramelizing onions; the slow, gradual process brings out their natural sweetness.
* **Celeriac:** One medium-sized celeriac (about 1 pound) is perfect for this recipe. Look for celeriac that is firm and heavy for its size. Peel it carefully and dice it into small cubes.
* **Butter:** Butter is essential for caramelizing the onions and building a rich flavor base. Use unsalted butter so you can control the saltiness of the soup.
* **Olive Oil:** A touch of olive oil helps to prevent the butter from burning and adds a subtle fruity note to the soup.
* **Beef Broth:** High-quality beef broth is the foundation of this soup. Look for a broth that is rich and flavorful. You can also use homemade beef broth for an even more intense taste. About 8 cups.
* **Dry Sherry (or Dry White Wine):** Sherry or white wine adds a touch of acidity and complexity to the soup. Dry sherry, such as Amontillado or Fino, is a great choice. If using white wine, opt for a dry variety like Sauvignon Blanc or Pinot Grigio. About 1/2 cup.
* **Fresh Thyme:** Fresh thyme adds a lovely herbaceous aroma to the soup. A few sprigs are all you need. You can also use dried thyme, but fresh thyme is preferred.
* **Bay Leaf:** A bay leaf adds a subtle depth of flavor to the broth. Don’t forget to remove it before serving.
* **Garlic:** A few cloves of garlic add a pungent aroma that compliments the other flavors beautifully. Use fresh cloves, finely minced or pressed.
* **Salt and Black Pepper:** Season to taste. Be generous with the salt, as it helps to bring out the flavors of the onions and celeriac.
* **Crusty Bread:** For serving. A baguette or sourdough bread works well. Slice it into thick rounds and toast them until golden brown.
* **Gruyere Cheese:** Gruyere is the classic cheese for French onion soup. It melts beautifully and has a nutty, slightly sweet flavor. You can also use other melting cheeses, such as Swiss or provolone. About 8 ounces, grated.
* **Optional:** A splash of balsamic vinegar can add a touch of brightness and acidity to balance the richness of the soup.

## Step-by-Step Instructions

Now that we have our ingredients, let’s get cooking! Here’s how to make this delicious French Onion & Celeriac Soup:

**Step 1: Prepare the Vegetables**

* Peel and thinly slice the onions. The thinner you slice them, the faster they will caramelize.
* Peel the celeriac and dice it into small, even cubes. This will ensure that it cooks evenly.
* Mince or press the garlic.

**Step 2: Caramelize the Onions**

* In a large, heavy-bottomed pot or Dutch oven, melt the butter and olive oil over medium-low heat.
* Add the sliced onions and a pinch of salt. Stir to coat the onions in the butter and oil.
* Cook the onions slowly, stirring occasionally, for about 45-60 minutes, or until they are deeply golden brown and caramelized. The key is to be patient and not rush the process. The onions should be very soft and sweet.
* If the onions start to stick to the bottom of the pot, add a tablespoon of water or broth to deglaze the pan. Scrape up any browned bits from the bottom of the pot, as these add a lot of flavor.

**Step 3: Add the Celeriac and Garlic**

* Once the onions are caramelized, add the diced celeriac and minced garlic to the pot.
* Cook for another 5-7 minutes, stirring occasionally, until the celeriac is slightly softened and the garlic is fragrant.

**Step 4: Deglaze the Pot**

* Pour in the dry sherry or dry white wine and bring to a simmer. Scrape up any browned bits from the bottom of the pot.
* Cook for 2-3 minutes, or until the alcohol has evaporated.

**Step 5: Add the Broth and Seasonings**

* Pour in the beef broth and add the fresh thyme sprigs and bay leaf.
* Bring the soup to a simmer, then reduce the heat and let it simmer for at least 30 minutes, or up to an hour, to allow the flavors to meld together. The longer it simmers, the more flavorful it will be.
* Season with salt and black pepper to taste. Remember that the broth may already be salty, so start with a small amount and add more as needed.

**Step 6: Remove the Thyme and Bay Leaf**

* Before serving, remove the thyme sprigs and bay leaf from the soup.
* If desired, add a splash of balsamic vinegar for extra brightness.

**Step 7: Prepare the Bread and Cheese**

* Preheat your broiler.
* Slice the baguette or sourdough bread into thick rounds and toast them until golden brown.
* Grate the Gruyere cheese.

**Step 8: Assemble and Broil the Soup**

* Ladle the soup into oven-safe bowls or ramekins.
* Top each bowl with a toasted bread slice and a generous amount of grated Gruyere cheese.
* Place the bowls under the broiler and broil for 2-3 minutes, or until the cheese is melted and bubbly and golden brown.
* Watch carefully to prevent the cheese from burning.

**Step 9: Serve and Enjoy!**

* Carefully remove the bowls from the broiler and let them cool slightly before serving.
* Serve immediately and enjoy the rich, comforting flavors of this French Onion & Celeriac Soup.

## Tips and Variations

* **Make it vegetarian:** Use vegetable broth instead of beef broth for a vegetarian version.
* **Add a touch of sweetness:** A teaspoon of brown sugar or maple syrup can enhance the sweetness of the caramelized onions.
* **Boost the flavor:** A tablespoon of Worcestershire sauce or soy sauce can add depth and umami to the broth. (Check ingredients for gluten if needed).
* **Add other vegetables:** Consider adding other root vegetables, such as carrots or parsnips, for even more flavor and texture.
* **Use different cheese:** If you don’t have Gruyere, you can use other melting cheeses like Swiss, provolone, or mozzarella.
* **Make it ahead:** The soup can be made ahead of time and stored in the refrigerator for up to 3 days. Reheat gently before serving. You can also freeze the soup for up to 2 months.
* **Slow Cooker Option:** Caramelize the onions as instructed in a skillet then transfer to your slow cooker. Add the remaining ingredients and cook on low for 6-8 hours or on high for 3-4 hours. Top with bread and cheese and broil as instructed before serving.
* **Instant Pot Version:** Use the saute function to caramelize the onions. Deglaze the pot, then add the remaining ingredients (except the bread and cheese). Cook on high pressure for 15 minutes, followed by a natural pressure release for 10 minutes. Top with bread and cheese and broil as instructed before serving.

## Serving Suggestions

This French Onion & Celeriac Soup is delicious on its own, but it also pairs well with:

* A simple green salad
* A grilled cheese sandwich
* A crusty loaf of bread for dipping

## Nutritional Information (Approximate)

*Note: Nutritional information can vary depending on specific ingredients and portion sizes.*

* Calories: 350-450 per serving
* Fat: 20-30g
* Saturated Fat: 12-18g
* Cholesterol: 80-100mg
* Sodium: 800-1200mg
* Carbohydrates: 30-40g
* Fiber: 5-7g
* Sugar: 10-15g
* Protein: 15-20g

## Frequently Asked Questions (FAQ)

**Q: Can I use a different type of onion?**

A: While yellow onions are traditional, you can experiment with other types, such as sweet onions, red onions, or shallots. Each will impart a slightly different flavor to the soup. A combination of onion types can also add complexity.

**Q: I don’t have celeriac. Can I leave it out?**

A: Yes, you can leave out the celeriac, but it does add a unique flavor and texture. If you omit it, you might want to add another root vegetable, such as a parsnip or carrot, for added depth.

**Q: Can I use dried thyme instead of fresh?**

A: Yes, you can use dried thyme. Use about 1 teaspoon of dried thyme for every tablespoon of fresh thyme called for in the recipe.

**Q: My soup is too salty. What can I do?**

A: If your soup is too salty, you can try adding a little bit of water or unsalted broth to dilute it. You can also add a pinch of sugar to help balance the saltiness.

**Q: Can I make this soup in a slow cooker?**

A: Yes, you can adapt this recipe for a slow cooker. Caramelize the onions in a skillet first, then transfer them to the slow cooker along with the remaining ingredients. Cook on low for 6-8 hours or on high for 3-4 hours. Top with bread and cheese and broil as instructed before serving.

**Q: Can I freeze this soup?**

A: Yes, this soup freezes well. Let it cool completely before transferring it to freezer-safe containers. Freeze for up to 2 months. Thaw overnight in the refrigerator before reheating.

## Conclusion

This French Onion & Celeriac Soup is a delightful twist on a classic, offering a richer, more complex flavor profile and a creamy texture that will leave you wanting more. The addition of celeriac elevates the soup to new heights, creating a dish that is both comforting and sophisticated. Whether you’re looking for a cozy weeknight meal or an elegant appetizer for a dinner party, this soup is sure to impress. So, gather your ingredients, put on some music, and enjoy the process of creating this culinary masterpiece. Bon appétit!

## Recipe Card

**French Onion & Celeriac Soup**

A flavorful twist on a classic French onion soup with the addition of celeriac for a creamy texture and earthy sweetness.

**Prep Time:** 20 minutes
**Cook Time:** 1 hour 30 minutes
**Total Time:** 1 hour 50 minutes
**Servings:** 6

**Ingredients:**

* 3 lbs yellow onions, thinly sliced
* 1 lb celeriac, peeled and diced
* 4 tbsp unsalted butter
* 2 tbsp olive oil
* 4 cloves garlic, minced
* 1/2 cup dry sherry or dry white wine
* 8 cups beef broth
* 2 sprigs fresh thyme
* 1 bay leaf
* Salt and pepper to taste
* 6 slices crusty bread, toasted
* 8 oz Gruyere cheese, grated
* Optional: Balsamic vinegar

**Instructions:**

1. In a large pot or Dutch oven, melt butter and olive oil over medium-low heat.
2. Add onions and salt. Cook, stirring occasionally, for 45-60 minutes, until caramelized.
3. Add celeriac and garlic. Cook for 5-7 minutes, until softened.
4. Deglaze with sherry or wine, scraping up browned bits.
5. Add beef broth, thyme, and bay leaf. Simmer for 30-60 minutes.
6. Remove thyme and bay leaf. Season with salt and pepper.
7. Preheat broiler. Ladle soup into oven-safe bowls.
8. Top with toasted bread and Gruyere cheese.
9. Broil for 2-3 minutes, until cheese is melted and bubbly.
10. Serve immediately.

**Notes:**

* For a vegetarian version, use vegetable broth.
* Make ahead: Soup can be refrigerated for up to 3 days or frozen for up to 2 months.